In general, a washing machine forcibly spins (moves, rotates) the laundry (a target to be washed, clothes) within a drum by using a mechanical force, such as a frictional force generated between the drum, which is rotated by a driving force transferred from a driving motor, and the laundry, after filling detergent, washing water and the laundry in the drum. Accordingly, the laundry can be washed by a physical reaction such as friction or impact. Also, the laundry which contacts the detergent can be washed by a chemical reaction with the detergent. The spinning (rotating, moving) of the laundry within the drum may facilitate the chemical reaction of the detergent.
A drum type washing machine, which has been widely used in recent time, has a rotation shaft of the drum formed in a horizontal direction. The rotation shaft of the drum is alternatively inclined with respect to the horizontal direction by a predetermined angle. The drum type washing machine having the horizontal rotation shaft allows the laundry to be spin along an inner circumferential surface of the drum in a circumferential direction.
The laundry is rotated along the inner circumferential surface of the drum by a centrifugal force responsive to the rotation of the drum and the friction against the inner circumferential surface of the drum. For assisting the spinning of the laundry, lifters are often provided on the inner circumferential surface of the drum. Here, the laundry also performs a circular motion along the inner circumferential surface according to rotation speed of the drum and a falling motion from an upper side of the drum by the force of gravity. The falling motion becomes a factor which greatly affects a washing effect.
The motion (rotation, spinning, movement) of the laundry within the drum greatly affects the washing effect. In detail, various types of motions of the laundry may change contact surfaces of the laundry, which rubs against the inner circumferential surface of the drum, resulting in an even washing of the laundry, and also allowing for an increase in a physical force applied to the laundry so as to enhance the washing effect.
Meanwhile, the washing machine is configured to run the rotation shaft by a driving motor, which has a rotor structure by use of permanent magnets. The permanent magnet motor typically includes a stator and a rotor. The stator is fixedly wound on the outside of the rotor. The rotor is in a circular shape, and has a plurality of permanent magnets regularly aligned in an annular form. Rotor teeth may be interposed between the adjacent permanent magnets so as to secure permanent magnets. Also, the rotor teeth form magnetic fluxes with the stator so as for the rotor to have a rotational force.
For the related art drum type washing machine, a single drum is rotated to make the laundry moved. Accordingly, the laundry is merely circulated from an initial position in the circumferential direction of the drum along the inner circumferential surface of the drum (i.e., merely generating a circumferential-direction motion), without complicated motions such as an axial-direction motion and a rotation motion. That is, the laundry generates the two-dimensional (monotonous) motion because there is no room for a separate external force applied to generate such complicated motions of the laundry. Consequently, the laundry is limitedly moved, which gives rise to a limited washing effect, and an increase in washing time and power consumption.
Furthermore, the related art washing machine causes a problem in that those clothes are stuck on the inner circumferential surface of the drum, with getting entangled together, after completion of washing and dehydration. Since the dehydration is performed using a centrifugal force by the rotation of the drum, the laundry in the entangled or twisted state is stuck on the inner circumferential surface of the drum. Hence, the laundry remains entangled until taken out of the washing machine for drying, thereby causing wrinkles on the laundry and difficulty in taking the laundry out of the washing machine.